ISP Decimator (Sabro version)

[motterpaul]

Before I post oics, etc a few basic questions for those who may know.

Woking on this: http://www.sabrotone.com/?attachment_id=1380

I did not notice I was out of 2n2222 so I am wondering if there is a decent sub?  ( I tried a 4403 and 3904). When I  power it up I get a sine-wave tone that varies in pitch as I turn the 1M trim. It is really pretty loud. I can hear the throughout but it is lower than unity.

For other parts I tried to get the closest pieces I could get:

The SIP chip I sourced for the THAT2181C is the CoolAudio 2181 - does anyone know if that should work? All the pinouts are the same.

For the LF353N I have LF353P

For the LF347 I have LF347N

Those are my questions. I believe my layout is otherwise correct.

Any ideas - thank you in advance!

[motterpaul]

Okay, I got this working now (yes, I had missed a cut), but I am still curious about the MPS2222a - is there a good substitute besides 2n2222a? (I have neither). This works but it also has a loud ring (like a 2k sine wave) all the time.

By the way - I didn't want to post the layout here because it belongs to Harold Sabro, but it looks like there is a cut behind R2, but I believe that is not intended. Anyway, I cut it but I bridged it also.

[motterpaul]

Ah - also - I only had a 5818 diode, not a 5819, which has a higher forward voltage. Would that matter?

So - I am petty confident about the chips now - it is just the MPS2222a and the 5819 - I need to know if I can use subs.

[pyreweb]

Hello Motterpaul,

I have just finished my own Decimator build, with the G-string add on. I subbed the MPS2222A for a 2N2222A, which I got 100 of on Amazon for under £2.

Mine does not work though.

[motterpaul]

Thank you for reminding me, I just in some 5819 diodes (I couldn't remember why). The last time I tried MY Decimator it had stopped working and I don't know why.

One thing that made a big difference was getting actual 1M trim pots - that was the one thing that made it almost work perfectly (I almost reached unity gain with no loss of tone). But the last time I tried it - no luck - meaning it still worked but with a substantial gain loss.

So - I just finished the MXR noise gate, which also did not work well until I got the exact transistor as specified. That one works almost exactly as well.

The weird thing is that every noise gate I have tried has eventually failed on me after a few weeks, except for the 1-knob which is uber-simple.

[larry]

But 1 knob noise gate just reduces volume...at least mine does...how did you fix yours?

[motterpaul]

My 1-knob noise gate? It acts like a full gate (on/off) - not just a reduction in volume. It has always worked that way.

The Ibanez noise buster is a hum reducer that is not a gate at all (it has just one knob, maybe that is what you are thinking?). That one worked nicely for me at first as well, but then after about a month I realized it just was not doing anything. I don't know why.

The ISP decimator is supposed to be like a hum reducer + a noise gate. But it seem more like just a gate to me, and it really was a tone sucker. Even when I got it optimized it still seemed to suck some tone, but the other gates do seem to be true (on/off) gates.

Both the Noise Buster and the ISP are such big builds I don't even feel like trying to fix them. So, I am now just using the MXR noise gate, and it is usable and effective. It is slightly more adjustable than the 1-knob, and it recovers faster, so it is more usable, but it is also just a gate (not a hum reducer).

[pyreweb]

I had not realised that the Decimator could be a tone sucker, I have had problems with noise gates doing that before. Hopefully the G-string addition will counter that to some extent. I do not yet think my Decimator is at the stage of working enough to consider changing the pot; anything other than hissing and clicking noises would be an improvement. I will work on debugging it over the next few days.

[motterpaul]

Yeah, that ISP was a big and challenging build, but it looked great when finished. But when I tried it out and was only marginally happening with the results it was a letdown. I am not sure it is worth building (I think it was almost $20 in parts with some unusual IC chips, etc.).

IMO, the MXR is better and much easier to make.

[strassercaster]

Man I wish I had seen this post last week. I finished boxing mine last night at about 2am. Didnt test it yet it was late and the kids were sleeping. I built the noise buster first as well.The Noise Buster is ok if you leave the knob all the way down. It barely cuts treble and reduces the hum and switch pops from other pedals a lot.  

I am also using the 2n2222a transistor for the decimator as well. Did you use the exact right THAT chip? I spent 8 bucks just for that chip. . I hope it works . Its about as big a build as a chorus pedal. It also takes so much longer doing the Sabrotone builds. The seperate layout for links and cuts are helpful. It saves lots of time and prevents lots of mistakes. Not to mention having to look down for the values I have looked at the wrong value in the list several times but I learned to triple check when doing the Sabro layouts. I am totally bummed now . I havent even tried it yet and its a bust ha ha. Hopefully it works but if it doesnt im not going to spend much time troubleshooting it . It sounds like a wasted build from what your saying. We have the same opinion on the Noise buster so im sure your right about this one as well. I cant see a simple transistor making all that much of a difference.


  so The mxr your using. Did you make it?

[strassercaster]

how did you add the g string board? I saw a layout for it the other night but wasnt sure how to hook it up. How did you tie it in?

[strassercaster]

The difference in forward voltage between the two diodes wont matter that much. Ill let you know if my build works. I was sick when i did the circuit board a couple weeks ago so idk if it will work or not. I always get nervous when I finish a build . Part of me is scared it wont work and I will spend hours and hours figuring it out. Ha ha I will test it tonight and see whats up with mine

[motterpaul]

Well, I hope you test boards before you box them. I changed out the diode and it did not help. This build worked fine for awhile as soon as I put in the 1M trimpot, so I boxed it up. But suddenly it didn't work any more (I have been finding this with more builds lately, I really don't get it).

{EDIT- I used the CoolAudio chip and it seemed to work fine), I bought three of them and got a discount, I think about $4 apiece.

I have a pn2222a transistor (as I recall), I did not do the g-string add-on (I am not sure what that does).

I did get the Ibanez noise buster working again, and I am using the MXR noise gate. Between the two of them my rig is pretty quiet so I am not worried about the decimator so much.

[strassercaster]

The thing is all noise gates and things like that suck. Thats why i thought i would try the isp it seemed like maybe this time a noise gate wouldnt suck since it has great reviews and is expensive . Its still a noise gate unfortunately.Anything that is turned on is going to alter your tone for better or worse. At best they are arent improving your tone they are eliminating frequencys

[rocket88]

Just going to repost what I said before about noise gates and suppressors.

that's part of the problem with noise gates and suppressors, it's in the way they work. what they do is try and remove the high pitch noise, but each works in a slightly different way. noise gates are like a clamp, so any sound above a certain point gets cut, as in kills those frequencies, and not just affect hiss/hum. suppressors on the other hand does not actually close like a clamp and work by filtering certain frequencies, with the intention of effecting only the hiss/hum.

There are very few devices made to remove hiss that don't affect tone, one being the original rocktron hush not the new one. As a whole these devices are a waste of time, IMHO. I think that some hiss is alright, and you should is part of the effects character, not to mention it adds some life. Most of the time the hiss is just the amplification of the normal hiss your pickups have. If you want to remove all hiss you're really better off getting pickups that are hissless, like EMGs. As I've also said before this is why some famous musicians use EMGs, like Zakk Wylde and Les Claypool. Wylde uses them not just for their distortion characteristics, but he can jack of the gain with his OD into his Marshall and have crystal clear crunch. Claypool on the other hand uses EMGs because with all his effects the EMGs prevent added noise so no matter how many effects he's got on his signal is crystal clear. From my experience, I literally bought a set of EMG bass pickups in my Claypool phase, and took them out in a week for traditional style pickups. They were noiseless, like earily noiseless, but the trade off was they where lifeless without using the right effects.

[motterpaul]

Well... I agree with you on how they work, but noise gates are very common tools in studios. Furthermore, if you ever play in a gigging band you find that some people (chick singers and sound men) are especially sensitive about any undue noise coming from amps.

Since I do use pedals I have heard the old line "if your amp knew the words it wouldn't have to hum all the time" joke more than a few time. So - I started using noise gates back in the 70s in studios, and with my guitar gear when I started playing in working bands.

I personally think the Ibanez noise buster (a filter) works great - as far as I can hear it does not eliminate any frequencies that I care about in terms of my guitar tone. I just checked my hearing and it only goes up to 11.5k (not bad for 62 y.o.) but then again a typical Celestion speaker's freq response begins to drop off significantly at 5k anyway. Every decent audio engineer knows that one of the best ways to reduce noise on lead guitar tracks is to roll off the uber-highs, because there really isn't that much audio content in that range.

As far as noise gates - yes, they clamp off when there is no musical signal. A good one (and I have tried many including several rack models) has a combination of very fine threshold setting capability along with a delay in turning off the noise (to let your delay trails ring out) combined with a very fast recovery for when one starts playing again.

Last night I plugged in my pedal board and I didn't even notice my MXR - noise gate was on until I had been playing for about 30 minutes. I used to use a branded MXR noise gate when I was gigging a few years ago. They work well.

I had high hopes for the ISP decimator, but it never sounded transparent enough for me. Online I have read that even the branded ones do not work all that well. But a good noise gate is different - the designers understand what it is supposed to do, and so far I am satisfied with what I have.

[rocket88]

There's nothing to agree or disagree about what I said in how noise gates and suppressors work, it's a fact. In all my years of playing live and recording, ~15yrs, I've never had a sound guy or studio engineer have an issue with noise from any pedal, even vintage fuzzes that have more hiss then you can even think. Not to mention, the thousands of shows I've been to and bands that I've met I've seen I can think of 1 that uses a gate or suppressor. Again, my opinion based on experience, and adding that they do affect your sound based on the electrical engineering knowledge I'll keep my instruments tone thank you.

[strassercaster]

ine is messed up. I triple checked everything before plugging it in. I dont have any mistakes. I have voltage readings in ther 3.8 range i do have a couple readings in the 1.8 range. the mps 2222 transistor is just a general purpose with 100-300 hfe. Im wondering if i got a bad that chip i used the 2181c cost like 7 bucks. I am bummed out because i cant find working voltages. I have know idea how these things work. There are 7 or 8 people that didnt get it too work and counting harold 3 that did. I either get nothing or total buzz noise when turning the trimpot.Im going to shelf it for now. Maybe ill make a mxr noise gate. I like the noise buster and it seems ok looking for a little better though.  use stacked humbuckers on my starts so 60 cycle is usually only a problem with computers and tvs . As my old foreman would say when he messed up AWE CAT SHIT

[strassercaster]

I agree. So you like the mxr noise gate? Did you make yours? Is there one with mods that are col to make? I was so excited to make this one and now after 6 hours and 25 bucks im bummed. Oh well I only have a few pedals in the trouble shooting pile right now out of 85 builds i can live with it.

[motterpaul]

Yeah, I like the MXR. It seems pretty transparent to me.